As used throughout this specification, the term "polyurea" is meant to embody the polycondensation product obtained from reaction of a compound containing an isocyanate functional group with a compound containing an active hydrogen functional group. It will be appreciated that "polyurea" encompasses modified and unmodified urea polymers As used throughout this specification, the term "modified polyurea" is meant to embody a urea polymer in which up to 50 percent of the polymer backbone forming linkages have been substituted. Examples of suitable substituents include urethane groups.
The compound containing an active hydrogen functional group may be selected from compounds having one or more groups selected from amino, amido, imino, olamino or combinations thereof disposed on a polymeric (eg. polyester, polyether, polyalkene) backbone. Moreover, any low molecular weight compound which comprises one or more of the functional groups discussed above will be suitable for use. In urethane modified polyureas, some of the active hydrogen is in a hydroxyl function form. The monomer containing an active hydrogen functional group may comprise from about 20 units up to about 25,000 units.
Generally, a urea is the product of a reaction between an isocyanate and an amine: ##STR1##
By using a di- or poly-functional isocyanate and a di- or poly-amine, a relatively high molecular weight polymer may be obtained: ##STR2##
In contract to the production of a urea, a urethane is the product of the reaction between an isocyanate and an alcohol: ##STR3## By using di- or poly-functional isocyanate and hydroxyl-terminated low molecular weight polymer, the production of a high molecular weight polyurethane may be achieved: ##STR4##
Thus, in order to obtain a high molecular weight polymer each of the isocyanate compound and the active hydrogen-containing compound (i.e. the amine for production of urea and the hydroxyl-terminated low molecular weight polymer for production of urethane) must contain a functionality of greater than 1.